1. Field of the Invention
The present invention relates to a structure for supporting a steering column of a vehicle and, more particularly, to a collapsible steering column supporting structure of a vehicle which prevents an occupant of the vehicle from sustaining injuries upon a collision of the vehicle.
2. Description of Related Art
A steering column typically passes through a hole or opening formed in a vehicle instrument panel structure constituting part of a front wall of a front compartment of the vehicle. The steering column conventionally extends through the opening formed in the instrument panel structure and towards a driver's seat, in front of which the instrument panel structure is located. Japanese Unexamined Utility Model Publication No. 2-69,554 discloses such a steering column extending through an opening in an instrument panel. In the steering column supporting structure disclosed by this publication, a meter hood panel, covering meters installed in the instrument panel structure, is shaped so as to form an upper wall defining an upper portion of the opening. A column cover, partially covering the steering column between the instrument panel and the steering wheel, is located close to the opening Such a steering column collapses axially towards the instrument panel upon a vehicle collision, so that the column cover abuts the instrument hood panel.
Collapsible steering columns are usually formed by two column portions These column portions are telescopically connected to each other via an impact absorption mechanism so as to allow the collapsible steering column to axially contract or collapse upon a collision of a vehicle During such a collapse, the steering column absorbs not only a primary impact, applied to a driver from the vehicle body, but also a secondary impact, such as a reaction force, developed on the steering column by the driver. Since the collapsible steering column must be installed in a limited vehicle body space, in which an engine and a transmission are disposed, and may have a force applied at its lower end by the engine and transmission during a collision of the vehicle, the steering column is connected to a pinion shaft of a steering gear unit by a flexible means, such as a cross joint, via a connecting shaft. The connecting shaft is connected to the collapsible steering column by the cross joint and is inclined downwards at an angle with respect to an imaginary line extending from the collapsible steering column. The connecting shaft, therefore, turns upwards during a collision of the vehicle, thereby preventing the collapsible steering column from being forced backwards and exerting a primary impact on the driver. Such a collapsible steering column is known from, for instance, Japanese Unexamined Utility Model Publication No. 63- 131,867.
If a collapsible steering column is intended to absorb both primary and secondary impacts, it is normally designed to have a long stroke of collapse However, since a column cover, partially covering the steering column between the instrument panel and the steering wheel, may crash into the meter hood if a serious steering column collapse occurs, the steering column is disabled from collapsing sufficiently to keep the driver safe, as it is intended to do. In addition, a sufficient clearance must be provided between an intermediate shaft of the column and an instrument panel or dashboard to allow backward movement of the engine and transmission during a collision of the vehicle without any interference with the dashboard. However, since a sealing collar, by which the intermediate shaft is supported in the dashboard, is integrally formed with ribs and flanges, the intermediate shaft is brought into abutment against the sealing collar before it abuts against the dashboard. Such forces the steering column itself, and hence the steering wheel secured to the top of the steering column, toward the driver. Such a sealing collar decreases substantially the clearance between the intermediate shaft and the dashboard.